Heretofore, as an outdoor-type transportable heater, a gas heater and a body warmer have been widely prevalent However, these products have been inconvenient in that only a portion of user's body is warmed up or the level of warmth cannot be controlled. Further, heated clothing and a mat, each of which uses a battery and has an electrically resistive element distributed thereinside and adapted to generate heat based on electrical energy from the battery, have come into practical use. However, a mass energy density of latest batteries is still not so high, and therefore it is unable to supply required heating energy for a sufficient period of time.
With a view to solving this problem, the inventor of this application proposed an invention disclosed in Japanese Patent No. 3088127. Another invention publicly known by and disclosed in Japanese Patent Laid-Open Publication No. 09-126423 has come into practical use. These inventions are intended to use LPG as an energy source so as to overcome a disadvantage of batteries, and designed to burn LPG using a catalyst and extract resulting heat. In the former invention, the extracted heat acts to activate a heat-driven pump so as to transfer the heat by the medium of water. In the latter invention, the heat transfer is achieved by air convection.
As compared with flaming combustion, catalytic combustion is a tough combustion reaction capable of being uninterruptedly continued only by supplying fuel and air while maintaining a certain level of high-temperature environment, even if the wind blows or an air-fuel mixture ratio is slightly changed. Further, the catalytic combustion has a feature such that combustion is induced at a lower temperature than that in the flaming combustion. However, if the reaction is continued at a theoretical mixture ratio for a longer period of time, a combustion temperature will be excessively increased to cause deterioration of the catalyst. Thus, it is necessary to produce the reaction at a learn mixture ratio (excess in air). This inevitably leads to lowering of the combustion temperature to cause the need for increasing a heat transfer area required for activating the heat-driven pump and thereby increasing the size of a combustion chamber. Thus, there remains a problem in terms of portability. Moreover, it is impossible to use an atmospheric burner in view of the need for introducing air in large excess. In contrast, the flaming combustion originally has a high combustion temperature. Thus, the required heat transfer area can be reduced to facilitate downsizing, and a surface area of a heat generation section can be reduced to restrict heat leakage from the surface to the outside so as to provide enhanced heat efficiency. However, it is practically difficult to perform combustion of a fully pre-mixed mixture (fully pre-mixed combustion) within a narrow space surrounded by a peripheral wall. Such combustion is further difficult for the atmospheric burner designed to inject LPG from a nozzle and suck air based on a momentum of the injected LPG. While a flame can be maintained at a rich mixture ratio, it will be blown off before the mixture ratio reaches the theoretical mixture ratio. While a fan is typically used for forcibly supplying air (forced air supply) to achieve the fully pre-mixed combustion, such a forced-air fan cannot be used in a portable apparatus pursuing downsizing, because it has to be rotated using a motor requiring a power source, such as a battery.